Amorphus silicon and germanium photoconductive member containing oxygen

ABSTRACT

A photoconductive member comprises a substrate for photoconductive member and a light receiving layer provided on said substrate having a layer constitution in which a layer region (G) comprising an amorphous material containing germanium atoms and a layer region (S) exhibiting photoconductivity comprising an amorphous material containing silicon atoms are successively provided from the substrate side, said light receiving layer having a layer region (O) containing oxygen atoms, the depth profile of oxygen atoms in said layer region (O) being increased smoothly and continuously toward the upper end surface of the light receiving layer.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a photoconductive member having sensitivity toelectromagnetic waves such as light [herein used in a broad sense,including ultraviolet rays, visible light, infrared rays, X-rays,gamma-rays, and the like].

2. Description of the Prior Art

Photoconductive materials, which constitute photoconductive layers insolid state image pickup devices, image forming members forelectrophotography in the field of image formation, or manuscriptreading devices and the like, are required to have a high sensitivity, ahigh SN ratio [photocurrent (I_(p))/dark current (I_(d))], spectralcharacteristics matching to those of electromagnetic waves to beirradiated, a rapid response to light, a desired dark resistance valueas well as no harm to human bodies during usage. Further, in a solidstate image pick-up device, it is also required that the residual imageshould easily be treated within a predetermined time. Particularly, incase of an image forming member for electrophotography to be assembledin an electrophotographic device to be used in an office as officeapparatus, the aforesaid safety characteristic is very important.

From the standpoint as mentioned above, amorphous silicon [hereinafterreferred to as a-Si] has recently attracted attention as aphotoconductive material. For example, German OLS Nos. 2746967 and2855718 disclose applications of a-Si for use in image forming membersfor electrophotography, and German OLS No. 2933411 discloses anapplication of a-Si for use in a photoelectric transducing readingdevice.

However, under the present situation, the photoconductive member of theprior art having photoconductive layers constituted of a-Si are furtherrequired to be improved in a balance of overall characteristicsincluding electrical, optical and photoconductive characteristics suchas dark resistance value, photosensitivity and response to light, etc.,and environmental characteristics during use such as humidityresistance, and further stability with the lapse of time.

For instance, when the above photoconductive member is applied in animage forming member for electrophotography, residual potential isfrequently observed to remain during use thereof if improvements tohigher photosensitivity and higher dark resistance are scheduled to beeffected at the same time. When such a photoconductive member isrepeatedly used for a long time, there will be caused variousinconveniences such as accumulation of fatigue by repeated uses or socalled ghost phenomenon wherein residual images are formed.

Further, a-Si has a relatively smaller coefficient of absorption of thelight on the longer wavelength side in the visible light region ascompared with that on the shorter wavelength side. Accordingly, inmatching to the semiconductor laser commercially applied at the presenttime, the light on the longer wavelength side cannot effectively beutilized, when employing a halogen lamp or a fluorescent lamp as thelight source. Thus, various points remain to be improved.

On the other hand, when the light irradiated is not sufficientlyabsorved in the photoconductive layer, but the amount of the lightreaching the substrate is increased, interference due to multiplereflection may occur in the photoconductive layer to become a cause for"unfocused" image, in the case when the substrate itself has a highreflectance for the light transmitted through the photoconductive layer.

This effect will be increased, if the irradiated spot is made smallerfor the purpose of enhancing resolution, thus posing a great problem inthe case of using a semiconductor laser as the light source.

Accordingly, while attempting to improve the characteristics of a-Simaterial per se on one hand, it is also required to make efforts toovercome all the problems as mentioned above in designing of thephotoconductive member on the other hand.

In view of the above points, the present invention contemplates theachievement obtained as a result of extensive studies madecomprehensively from the standpoints of applicability and utility ofa-Si as a photoconductive member for image forming members forelectrophotography, solid state image pick-up devices, reading devices,ets. It has now been found that a photoconductive member having a layerconstitution comprising a light receiving layer exhibitingphotoconductivity, which comprises an amorphous material containingsilicon atoms as the matrix (a-Si), especially an amorphous materialcontaining at least one of hydrogen atom (H) and halogen atom (X) in amatrix of silicon atoms such as so called hydrogenated amorphoussilicon, halogenated amorphous silicon, or halogen-containinghydrogenated amorphous silicon [hereinafter referred to comprehensivelyas a-Si(H,X)], said photoconductive member being prepared by designingso as to have specific structure as hereinafter described, not onlyexhibits commercially excellent characteristics but also surpass thephotoconductive members of the prior art in substantially all respects,expecially having markedly excellent characteristics as aphotoconductive member for electrophotography and also excellentabsorption spectrum characteristics on the longer wavelength side.

SUMMARY OF THE INVENTION

A primary object of the present invention is to provide aphotoconductive member having electrical, optical and photoconductivecharacteristics which are constantly stable and all-environment typewith virtually no dependence on the environment is use, which member ismarkedly excellent in photosensitive characteristics on the longerwavelength side and light fatigue resistance and also excellent indurability without causing deterioration phenomenon when usedrepeatedly, exhibiting no or substantially no residual potentialobserved.

Another object of the present invention is to provide a photoconductivemember which is high in photosensitivity throughout the whole visiblelight region, particularly excellent in matching to a semiconductorlaser as well as in interference inhibition, and also rapid in responseto light.

Still another object of the present invention is to provide aphotoconductive member having sufficient charge retentivity duringcharing treatment for formation of electrostatic images to the extentsuch that a conventional electrophotographic method can be veryeffectively applied when it is provided for use as an image formingmember for electrophotography.

Further, still another object of the present invention is to provide aphotoconductive member for electrophotography, which can easily providean image of high quality which is high in density, clear in halftone andhigh in resolution.

Still another object of the present invention is to provide aphotoconductive member having high photosensitivity and high SN ratiocharacteristics.

According to the present invention, there is provided a photoconductivemember comprising a substrate for photoconductive member and a lightreceiving layer provided on said substrate having a layer constitutionin which a layer region (G) comprising an amorphous material containinggermanium atoms and a layer region (S) exhibiting photoconductivitycomprising an amorphous material containing silicon atoms aresuccessively provided from the substrate side, said light receivinglayer having a layer region (O) containing oxygen atoms, the depthprofile of oxygen atoms in said layer region (O) being increasedsmoothly and continuously toward the upper end surface of the lightreceiving layer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic sectional view for illustration of the layerconstitution of the photoconductive member according to the presentinvention;

FIGS. 2 to 10 each shows a schematic illustration of the depth profilesof germanium in the light receiving layer;

FIGS. 11 to 16 each shows a schematic illustration of the depth profileof oxygen atoms in the light receiving layer;

FIG. 17 is a schematic illustration of the device used in the presentinvention; and

FIGS. 18 and 19 each shows a distribution of the respective atoms inExamples of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings, the photoconductive members according tothe present invention are to be described in detail below.

FIG. 1 shows a schematic sectional view for illustration of the layerconstitution of a first embodiment of the photoconductive member of thisinvention.

The photoconductive member 100 as shown in FIG. 1 is constituted of alight receiving layer 102 formed on a substrate 101 for photoconductivemember, said light receiving layer 102 having a free surface 105 on oneend surface.

The light receiving layer 102 is constituted of a first layer region (G)103 consisting of germanium atoms and, if desired, at least one ofsilicon atoms, hydrogen atoms and halogen atoms (hereinafter abbreviatedas "a-Ge(Si,H,X)" and a second layer region (S) 104 havingphotoconductivity laminated successively from the substrate side 101.

The germanium atoms contained in the first layer region (G) 103 may becontained uniformly throughout the layer region (G) 103, oralternatively with ununiform depth profile in the layer thicknessdirection. However, in either case, in the interplanar directionparallel to the surface, they are required to be contained evenly with auniform distribution for uniformizing the characteristics within theinterplanar direction. In particular, the germanium atoms are containedin the first layer region (G) 103 so that they are contained evenly inthe layer thickness direction of the light receiving layer 102 and in adistribution more enriched toward the substrate side 101 with respect tothe side opposite to the side where the substrate is provided (thesurface side 105 of the light receiving layer 102) or in a distributionopposite to such a distribution.

In the photoconductive member of the present invention, the distributionof germanium atoms contained in the first layer region (G) as describedabove should desirably take such a profile in the layer thicknessdirection, while a uniform distribution within the plane parallel to thesurface of the substrate.

In the present invention, in the second layer region (S) provided on thefirst layer region (G), no germanium atom is contained, and by formingthe light receiving layer to such a layer constitution, it is possibleto give a photoconductive member which is excellent in photosensitivityto the light over the entire wavelength region from relatively shorterwavelength to relatively longer wavelength including visible lightregion.

Also, in a preferred embodiment, since the distribution of germaniumatoms in the first layer region (G) is varied such that germanium atomsare distributed continuously over all the layer region with the contentC of germanium atoms in the layer thickness direction being reduced fromthe substrate side to the second layer region (S), affinity between thefirst layer region (G) and the second layer region (S) is excellent.Also, as described hereinafter, by increasing the content C of germaniumatoms at the end portion on the substrate side extremely great, thelight on the longer wavelength side which cannot substantially beabsorbed by the second layer region (S) can be absorbed in the firstlayer region (G) substantially completely, when employing asemiconductor laser, whereby interference by reflection from thesubstrate surface can be prevented.

Also, in the photoconductive member of the present invention, therespective amorphous materials constituting the first layer region (G)and the second layer region (S) have the common constituent of siliconatoms, and therefore chemical stability can be sufficiently ensured atthe laminated interface.

FIGS. 2 through 10 show typical examples of ununiform distribution inthe direction of layer thickness of germanium atoms contained in thefirst layer region (G) of the photoconductive member in the presentinvention.

In FIGS. 2 through 10, the abscissa indicates the content C of germaniumatoms and the ordinate the layer thickness of the first layer region(G), t_(B) showing the position of the end surface of the first layerregion (G) on the substrate side and t_(T) the position of the endsurface of the first layer region (G) on the side opposite to thesubstrate side. That is, layer formation of the first layer region (G)containing germanium atoms proceeds from the t_(B) side toward the t_(T)side.

In FIG. 2, there is shown a first typical embodiment of the depthprofile of germanium atoms in the layer thickness direction contained inthe first layer region (G).

In the embodiment as shown in FIG. 2, from the interface position t_(B)at which the surface, on which the first layer region (G) containinggermanium atoms is to be formed, is contacted with the surface of saidlayer region (G) to the position t₁, germanium atoms are contained inthe first layer region (G) as formed, while the content C of germaniumatoms taking a constant value of C₁, which content being graduallydecreased from the content C₂ continuously from the position t₁ to theinterface position t_(T). At the interface position t_(T), the content Cof germanium atoms is made C₃.

In the embodiment shown in FIG. 3, the content C of germanium atomscontained is decreased gradually and continuously from the positiont_(B) to the position t_(T) from the content C₄ until it becomes thecontent C₅ at the position t_(T).

In case of FIG. 4, the content C of germanium atoms is made constant asC₆, gradually decreased continuously from the position t₂ to theposition t_(T), and the content C is made substantially zero at theposition t_(T) (substantially zero herein means the content less thanthe detectable limit).

In case of FIG. 5, the content C of germanium atoms are decreasedgradually and continuously from the position t_(B) to the position t_(T)from the content C₈, until it is made substantially zero at the positiont_(T).

In the embodiment shown in FIG. 6, the content C of germanium atoms isconstantly C₉ between the position t_(B) and the position t₃, and it ismade C₁₀ at the position t_(T). Between the position t₃ and the positiont_(T), the content is reduced as a first order function from theposition t₃ to the position t_(T).

In the embodiment shown in FIG. 7, there is formed a depth profile suchthat the content C take a constant value of C₁₁ from the position t_(B)to the position t₄, and is decreased as a first order function from thecontent C₁₂ to the content C₁₃ from the position t₄ to the positiont_(T).

In the embodiment shown in FIG. 8, the content C of germanium atoms isdecreased as a first order function from the content C₁₄ to zero fromthe position t_(B) to the position t_(T).

In FIG. 9, there is shown an embodiment, where the content C ofgermanium atoms is decreased as a first order function from the contentC₁₅ to the content C₁₆ from the position t_(B) to t₅ and made constantlyat the content C₁₆ between the position t₅ and t_(T).

In the embodiment shown in FIG. 10, the content C of germanium atoms isat the content C₁₇ at the position t_(B), which content C₁₇ is initiallydecreased gradually and abruptly near the position t₆ to the positiont₆, until it is made the content C₁₈ at the position t₆.

Between the position t₆ and the position t₇, the content C is initiallydecreased abruptly and thereafter gradually, until it is made thecontent C₁₉ at the position t₇. Between the position t₇ and the positiont₈, the content C is decreased very gradually to the content C₂₀ at theposition t₈. Between the position t₈ and the position t_(T), the contentis decreased along the curve having a shape as shown in the Figure fromthe content C₂₀ to substantially zero.

As described above about some typical examples of depth profiles ofgermanium atoms contained in the first layer region (G) in the directionof the layer thickness by referring to FIGS. 2 through 10, as apreferable embodiment in the present invention, the first layer region(G) is provided desirably in a depth profile so as to have a portionenriched in content C of germanium atoms on the substrate side and aportion depleted in content C of germanium atoms to considerably lowerthan that of the substrate side on the interface t_(T) side.

The first layer region (G) constituting the light receiving layer of thephotoconductive member in the present invention may preferably beprovided so as to have a localized region (A) containing germanium atomsat a relatively higher content on the substrate side, or contrariwise onthe free surface side.

For example, the localized region (A), as explained in terms of thesymbols shown in FIG. 2 through FIG. 10, may be desirably providedwithin 5μ from the interface position t_(B).

In the present invention, the above localized region (A) may be made tobe identical with the whole layer region (L_(T)) up to the depth of 5μthickness from the interface position t_(B), or alternatively a part ofthe layer region (L_(T)).

It may suitably be determined depending on the characteristics requiredfor the light receiving layer to be formed, whether the localized region(A) is made a part or whole of the layer region (L_(T)).

The localized region (A) may preferably be formed according to such alayer formation that the maximum Cmax of the content of germanium atomsin a distribution in the layer thickness direction (depth profilevalues) may preferably be 1000 atomic ppm or more, more preferably 5000atomic ppm or more, most preferably 1×10⁴ atomic ppm or more based onthe sum of germanium atoms and silicon atoms.

That is, according to the present invention, the layer region containinggermanium atoms is formed so that the maximum value Cmax of the depthprofile may exist within a layer thickness of 5μ from the substrate side(the layer region within 5μ thickness from t_(B)).

In the present invention, the content of germanium atoms in the firstlayer region (G) containing germanium atoms, which may suitably bedetermined as desired so as to achieve effectively the objects of thepresent invention, may preferably be 1 to 10×10⁵ atomic ppm, morepreferably 100 to 9.5×10⁵ atomic ppm, most preferably 500 to 8×10⁵atomic ppm.

In the photoconductive member of the present invention, the layerthickness of the first layer region (G) and the thickness of the secondlayer region (S) are one of important factors for accomplishingeffectively the object of the present invention and therefore sufficientcare should be paid in designing of the photoconductive member so thatdesirable characteristics may be imparted to the photoconductive memberformed.

In the present invention, the layer thickness T_(B) of the first layerregion (G) may preferably be 30 Å to 50μ, more preferably 40 Å to 40μ,most preferably 50 Å to 30μ.

On the other hand, the layer thickness T of the second layer region (S)may be preferably 0.5 to 90μ, more preferably 1 to 80μ, most preferably2 to 50μ.

The sum of the layer thickness T_(B) of the first layer region (G) andthe layer thickness T of the second layer region (S), namely (T_(B) +T)may be suitably determined as desired in designing of the layers of thephotoconductive member, based on the mutual organic relationship betweenthe characteristics required for both layer regions and thecharacteristics required for the whole light receiving layer.

In the photoconductive member of the present invention, the numericalrange for the above (T_(B) +T) may generally be from 1 to 100μ,preferably 1 to 80μ, most preferably 2 to 50μ.

In a more preferred embodiment of the present invention, it is preferredto select the numerical values for respective thicknesses T_(B) and T asmentioned above so that the relation of T_(B) /T≦1 may be satisfied.

More preferably, in selection of the numerical values for thethicknesses T_(B) and T in the above case, the values of T_(B) and Tshould preferably be determined so that the relation T_(B) /T≦0.9, mostpreferably, T_(B) /T≦0.8, may be satisfied.

In the present invention, when the content of germanium atoms in thefirst layer region (G) is 1×10⁵ atomic ppm or more, the layer thicknessT_(B) of of the first layer region (G) should desirably be made as thinas possible, preferably 30μ or less, more preferably 25μ or less, mostpreferably 20μ or less.

In the present invention, illustrative of halogen atoms (X), which mayoptionally be incorporated in the first layer region (G) and/or thesecond layer region (S) constituting the light receiving layer, arefluorine, chlorine, bromine and iodine, particularly preferably fluorineand chlorine.

In the photoconductive member of the present invention, for the purposeof improvements to higher photosensitivity, higher dark resistance and,further, improvement of adhesion between the substrate and the lightreceiving layer, a layer region (O) containing oxygen atoms is providedin the light receiving layer. The oxygen atoms contained in the lightreceiving layer may be contained either evenly throughout the wholelayer region of the light receiving layer or locally only in a part ofthe layer region of the light receiving layer.

In the present invention, the distribution of oxygen atoms in the layerregion (O) may be such that the content C(O) is uniform within the planeparallel to the surface of the substrate, but the depth profile C(O) inthe layer thickness direction is ununiform similarly as the depthprovile of the germanium atoms as described with reference to FIGS. 2 to10.

FIGS. 11 through 16 show typical examples of distributions of oxygenatoms as a whole within the light receiving layer. In these Figures, theabscissa indicates the depth profile of the oxygen atoms in the layerthickness direction and the ordinate the layer thickness of the lightreceiving layer exhibiting photoconductivity, t_(B) showing the positionof the end surface (lower end surface) of the light receiving layer onthe substrate side and t_(T) the position of the end surface (upper endsurface) of the light receiving layer on the side opposite to thesubstrate side. That is, layer formation of the light receiving layerproceeds from the t_(B) side toward the t_(T) side.

In the embodiment as shown in FIG. 11, no oxygen atom is contained inthe layer region from the position t_(B) to the position t₉, the oxygenatoms are contained in the layer region (O) formed, while the contentC(O) of oxygen atoms being gradually increased continuously from theposition t₉ toward the t_(T) side. At the position t_(T), the contentC(O) of oxygen atoms C₂₁.

In the embodiment shown in FIG. 12, oxygen atoms are containedthroughout the whole layer region of the light receiving layer from theposition t_(B) to the free surface t_(T), with the content C(O) ofoxygen atoms being monotonously increased gradually and smoothly up tot_(T), until it becomes the content C₂₂ at the position t_(T).

In the embodiment shown in FIG. 13, the content C(O) of oxygen atoms isincreased monotonously from 0 to C₂₃ in the layer region from theposition t_(B) to t₁₀, while the content C(O) of oxygen atoms beingconstant as C₂₃ in the layer region from the position t₁₀ to t_(T).

In the embodiment shown in FIG. 14, the content C(O) of oxygen atoms isgently decreased from C₂₄ to C₂₅ in the layer region from the positiont_(B) to t₁₁, the content C(O) is constantly C₂₅ in the layer regionfrom the position t₁₁ to t₁₂, and the content C(O) of oxygen atomscontinuously increased from C₂₅ to C₂₆ in the layer region from theposition t₁₂ to t_(T).

In the embodiment shown in FIG. 15, there is shown the case of havingtwo layer regions (O) containing oxygen atoms. More specifically, in thelayer region from the position t_(B) to t₁₃, the content C(O) of oxygenatoms is decreased from C₂₇ to 0, no oxygen atom is contained in thelayer region from the position t₁₃ to t₁₄, and the content C(O) ismonotonously increased from 0 to C₂₈.

In the case of FIG. 16, the content C(O) of oxygen atoms is constantlyC₂₉ in the layer region from the position t_(B) to t₁₅ while the contentin the layer region from the position t₁₅ to t_(T) is slowly increasedinitially and thereafter increased abruptly until it reaches C₃₀ att_(T).

In the present invention, the layer region (O) containing oxygen atomsprovided in the light receiving layer, when improvements ofphotosensitivity and dark resistance are primarily intended, is providedso as to comprise the whole layer region of the light receiving layer,while it is provided in the vicinity of the free surface for preventionof injection of charges from the free surface of the light receivinglayer, or it is provided so as to occupy the layer region (E) in the endportion of the light receiving layer on the substrate side, whenreinforcement of adhesion between the substrate and the light receivinglayer is primarily intended.

In the first case, the content of oxygen atoms in the layer region (O)may be desirably made relatively smaller in order to maintain highphotosensitivity, while in the second case, the content is increased inthe vicinity of the surface for prevention of injection of charges fromthe free surface of the light receiving layer, and in the third case,the content is made relatively large for ensuring reinforcement ofadhesion with the substrate.

Also, for the purpose of accomplishing all of the three cases at thesame time, oxygen atoms may be distributed in the layer region (O) sothat they may be distributed in a relatively higher content on thesubstrate side, in a relatively lower content in the middle of the lightreceiving layer, with increased amount of oxygen atoms in the surfacelayer region on the free surface side of the light receiving layer.

In the present invention, the content of oxygen atoms to be contained inthe layer region (O) provided in the light receiving layer may besuitably selected depending on the characteristics required for thelayer region (O) per se or, when said layer region (O) is provided indirect contact with the substrate, depending on the organic relationshipsuch as the relation with the characteristics at the contacted interfacewith said substrate and others.

When, another layer region is to be provided in direct contact with saidlayer region (O), the content of oxygen atoms may be suitably selectedalso with considerations about the characteristics of said another layerregion and the relation with the characteristics of the contactedinterface with said another layer region.

The content of oxygen atoms in the layer region (O), which may suitablybe determined as desired depending on the characteristics required forthe photoconductive member to be formed, may be preferably 0.001 to 50atomic %, more preferably 0.002 to 40 atomic %, most preferably 0.003 to30 atomic %.

In the present invention, when the layer region (O) comprises the wholeregion of the light receiving layer or when, although it does notcomprise the whole layer region, the layer thickness To of the layerregion (O) is sufficiently large relative to the layer thickness T ofthe light receiving layer, the upper limit of the content of oxygenatoms in the layer region (O) should desirably be sufficiently smallerthan the aforesaid value.

In the case of the present invention, in such a case when the ratio ofthe layer thickness To of the layer region (O) relative to the layerthickness T of the light receiving layer is 2/5 or higher, the upperlimit of the content of oxygen atoms in the layer region (O) maypreferably be 30 atomic % or less, more preferably 20 atomic % or less,most preferably 10 atomic % or less.

In the present invention, the layer region (O) containing oxygen atomsfor constituting the light receiving layer may preferably be provided soas to have a localized region (B) containing oxygen atoms at arelatively higher content on the substrate side and in the vicinity ofthe free surface as described above, and in this case adhesion betweenthe substrate and the light receiving layer can be further improved, andimprovement of accepting potential can also be effected.

The localized region (B), as explained in terms of the symbols shown inFIGS. 11 to 16, may be desirably provided within 5μ from the interfaceposition t_(B) or the free surface t_(T).

In the present invention, the above localized region (B) may be made tobe identical with the whole layer region (L_(T)) up to the depth of 5μthickness from the interface position t_(B) or the free surface t_(T),or alternatively a part of the layer region (L_(T)).

It may suitably be determined depending on the characteristics requiredfor the light receiving layer to be formed, whether the localized regionis made a part or whole of the layer region (L_(T)).

The localized region (B) may preferably be formed according to such alayer formation that the maximum Cmax of the content of oxygen atoms ina distribution in the layer thickness direction may preferably be 500atomic ppm or more, more preferably 800 atomic ppm or more, mostpreferably 1000 atomic ppm or more.

That is, according to the present invention, the layer region (O)containing oxygen atoms is formed so that the maximum value Cmax of thedepth profile may exist within a layer thickness of 5μ from thesubstrate side or the free surface (the layer region within 5μ thicknessfrom t_(B) or t_(T)).

In the present invention, formation of the first layer region (G)constituted of a-Ge(Si,H,X) may be conducted according to the vacuumdeposition method utilizing discharging phenomenon, such as glowdischarge method, sputtering method or ion-plating method. For example,for formation of the first layer region (G) constituted of a-Ge(Si,H,X)according to the glow discharge method, the basic procedure comprisesintroducing a starting gas for Ge supply capable of supplying germaniumatoms (Ge) optionally together with a starting gas for Si supply capableof supplying silicon atoms (Si), and a starting gas for introduction ofhydrogen atoms (H) and/or a starting gas for introduction of halogenatoms (X) into a deposition chamber which can be internally brought to areduced pressure, and forming a plasma atmosphere of these gases byexciting glow discharge in said deposition chamber, thereby forming alayer consisting of a-Ge(Si,H,X) on the surface of a substrate set at apredetermined position. For incorporation of germanium atoms in anununiform depth profile, the content of germanium atoms may becontrolled following a desired change rate curve in formation of thelayer comprising a-Ge(Si,H,X). Alternatively, for formation according tothe sputtering method, by use of a target constituted of Si or twosheets of targets of said target and a target constituted of Ge, or atarget of a mixture of Si and Ge in an atmosphere of an inert gas suchas Ar, He, etc. or a gas mixture based on these gases, a starting gasfor Ge supply optionally diluted with a diluting gas such as He, Ar,etc. and together with, if desired, a gas for introduction of hydrogenatoms (H) and/or halogen atoms (X) may be introduced into a depositionchamber for sputtering and a plasma atomsphere of desired gases areformed. For making the distribution of germanium atoms ununiform, forexample, the flow rate of the starting gas for Ge supply may becontrolled according to the change rate curve as desired in carrying outsputtering of the target.

The starting gas for supplying Si to be used in the present inventionmay include gaseous or gasifiable hydrogenated silicons (silanes) suchas SiH₄, Si₂ H₆, Si₃ H₈, Si₄ H₁₀ and others as effective materials. Inparticular, SiH₄ and Si₂ H₆ are preferred with respect to easy handlingduring layer formation and efficiency for supplying Si.

As the substances which can be starting gases for Ge supply, there maybe effectively employed or gaseous or gasifiable hydrogenated germaniumsuch as GeH₄, Ge₂ H₆, Ge₃ H₈, Ge₄ H₁₀, Ge₅ H₁₂, Ge₆ H₁₄, Ge₇ H₁₆, Ge₈H₁₈, Ge₉ H₂₀, etc. In particular, GeH₄, Ge₂ H₆ and Ge₃ H₈ are preferredwith respect to easy handling during layer formation and efficiency forsupplying Ge.

Effective starting gases for introduction of halogen atoms to be used inthe present invention may include a large number of halogenic compounds,as exemplified preferably by gaseous or gasifiable halogenic compoundssuch as halogenic gases, halides, interhalogen compounds, silanederivatives substituted with halogens and others.

Further, there may also be included gaseous or gasifiable siliconcompounds containg halogen atoms constituted of silicon atoms andhalogen atoms as constituent elements as effective ones in the presentinvention.

Typical examples of halogen compounds preferably used in the presentinvention may include halogen gases such as of fluorine, chlorine,bromine or iodine, interhalogen compounds such as BrF, ClF, ClF₃, BrF₅,BrF₃, IF₃, IF₇, ICl, IBr, etc.

As the silicon compounds containing halogen atoms, namely so calledsilane derivatives substituted with halogens, there may preferably beemployed silicon halides such as SiF₄, Si₂ F₆, SiC1₄, SiBr₄ and thelike.

When the characteristic photoconductive member of the present inventionis formed according to the glow discharge method by employment of such asilicon compound containing halogen atoms, it is possible to form thefirst layer region (G) comprising a-SiGe containing halogen atoms on adesired substrate without use of a hydrogenated silicon gas as thestarting gas capable of supplying Si together with the starting gas forGe supply.

In the case of forming the first layer region (G) containing halogenatoms according to the glow discharge method, the basic procedurecomprises introducing, for example, a silicon halide as the starting gasfor Si supply, a hydrogenated germanium as the starting gas for Gesupply and a gas such as Ar, H₂, He, etc. at a predetermined mixingratio into the deposition chamber for formation of the first layerregion (G) and exciting glow discharge to form a plasma atmosphere ofthese gases, whereby the first layer region (G) can be formed on adesired substrate. In order to control the ratio of hydrogen atomsincorporated more easily, hydrogen gas or a gas of a silicon compoundcontaining hydrogen atoms may also be mixed with these gases in adesired amount to form the layer.

Also, each gas is not restricted to a single species, but multiplespecies may be available at any desired ratio.

For formation of the first layer region (G) comprising a-Ge(Si,H,X)according to the ion-plating method, a vaporizing source such as apolycrystalline silicon or a single crystalline silicon and apolycrystalline germanium or a single crystalline germanium may beplaced in an evaporating boat, and the vaporizing source is heated bythe resistance heating method or the electron beam method (EB method) tobe vaporized, and the flying vaporized product is permitted to passthrough a desired gas plasma atmosphere.

In either case of the sputtering method and the ion-plating method,introduction of halogen atoms into the layer formed may be performed byintroducing the gas of the above halogen compound or the above siliconcompound containing halogen atoms into a deposition chamber and forminga plasma atmosphere of said gas.

On the other hand, for introduction of hydrogen atoms, a starting gasfor introduction of hydrogen atoms, for example, H₂ or gases such assilanes and/or hydrogenated germanium as mentioned above, may beintroduced into a deposition chamber for sputtering, followed byformation of the plasma atmosphere of said gases.

In the present invention, as the starting gas for introduction ofhalogen atoms, the halides or halo-containing silicon compounds asmentioned above can effectively be used. Otherwise, it is also possibleto use effectively as the starting material for formation of the layerregion (G) gaseous or gasifiable substances, including halidescontaining hydrogen atom as one of the constituents, e.g. hydrogenhalide such as HF, HCl, HBr, HI, etc.; halo-substituted hydrogenatedsilicon such as SiH₂ F₂, SiH₂ I₂, SiH₂ Cl₂, SiHCl₃, SiH₂ Br₂, SiHBr₃,etc.; hydrogenated germanium halides such as GeHF₃, GeH₂ F₂, GeH₃ F,GeHCl₃, GeH₂ Cl₂, GeH₃ Cl, GeHBr₃, GeH₂ Br₂, GeH₃ Br, GeHI₃, GeH₂ I₂,GeH₃ I, etc.; germanium halides such as GeF₄, GeCl₄, GeBr₄, GeI₄, GeF₂,GeCl₂, GeBr₂, GeI₂, etc.

Among these substances, halides containing hydrogen atoms can preferablybe used as the starting material for introduction of halogen atoms,because hydrogen atoms, which are very effective for controllingelectrical or photoelectric characteristics, can be introduced into thelayer simultaneously with introduction of halogen atoms during formationof the first layer region (G).

For introducing hydrogen atoms structurally into the first layer region(G), other than those as mentioned above, H₂ or a hydrogenated siliconsuch as SiH₄, Si₂ H₆, Si₃ H₈, Si₄ H₁₀, etc. together with germanium or agermanium compound for supplying Ge, or a hydrogenated germanium such asGeH₄, Ge₂ H₆, Ge₃ H₈, Ge₄ H₁₀, Ge₅ H₁₂, Ge₆ H₁₄, Ge₇ H₁₆, Ge₈ H₁₈, Ge₉H₂₀, etc. together with silicon or a silicon compound for supplying Sican be permitted to co-exist in a deposition chamber, followed byexcitation of discharging.

According to a preferred embodiment of the present invention, the amountof hydrogen atoms (H) or the amount of halogen atoms (X) or the sum ofthe amounts of hydrogen atoms and halogen atoms (H+X) to be contained inthe first layer region (G) constituting the light receiving layer to beformed should preferably be 0.01 to 40 atomic %, more preferably 0.05 to30 atomic %, most preferably 0.1 to 25 atomic %.

For controlling the amount of hydrogen atoms (H) and/or halogen atoms(X) to be contained in the first layer region (G), for example, thesubstrate temperature and/or the amount of the starting materials usedfor incorporation of hydrogen atoms (H) or halogen atoms (X) to beintroduced into the deposition device system, discharging power, etc.may be controlled.

In the present invention, for formation of the second layer region (S)constituted of a-Si(H,X), the starting materials (I) for formation ofthe first layer region (G), from which the starting material for thestarting gase for supplying Ge is omitted, are used as the startingmaterials (II) for formation of the second layer region (S), and layerformation can be effected following the same procedure and conditions asin formation of the first layer region (G).

More specifically, in the present invention, formation of the secondlayer region (S) constituted of a-Si(H,X) may be carried out accordingto the vacuum deposition method utilizing discharging phenomenon such asthe glow discharge method, the sputtering method or the ion-platingmethod. For example, for formation of the second layer region (S)constituted of a-Si(H,X), the basic procedure comprises introducing astarting gas for Si supply capable of supplying silicon atoms asdescribed above, optionally together with starting gases forintroduction of hydrogen atoms (H) and/or halogen atoms (X), into adeposition chamber which can be brought internally to a reduced pressureand exciting glow discharge in said deposition chamber, thereby forminga layer comprising a-Si(H,X) on a desired substrate placed at apredetermined position. Alternatively, for formation according to thesputtering method, gases for introduction of hydrogen atoms (H) and/orhalogen atoms (X) may be introduced into a deposition chamber forsputtering when effecting sputtering of a target constituted of Si in aninert gas such as Ar, He, etc. or a gas mixture based on these gases.

In the present invention, the amount of hydrogen atoms (H) or the amountof halogen atoms (X) or the sum of the amounts of hydrogen atoms andhalogen atoms (H+X) to be contained in the second layer region (S)constituting the light receiving layer to be formed should preferably be1 to 40 atomic %, more preferably 5 to 30 atomic %, most preferably 5 to25 atomic %.

In the present invention, for provision of the layer region (O)containing oxygen atoms in the light receiving layer, a startingmaterial for introduction of oxygen atoms may be used together with thestarting material for formation of the light receiving layer asmentioned above during formation of the layer and may be incorporated inthe layer while controlling their amounts.

When the glow discharge method is to be employed for formation of thelayer region (O), the starting material as the starting gas forformation of the layer region (O) may be constituted by adding astarting material for introduction of oxygen atoms to the startingmaterial selected as desired from those for formation of the lightreceiving layer as mentioned above. As such a starting material forintroduction of oxygen atoms, there may be employed most of gaseous orgasifiable substances containing at least oxygen atoms as constituentatoms.

For example, there may be employed a mixture of a starting gascontaining silicon atoms (Si) as constituent atoms, a starting gascontaining oxygen atoms (O) as constituent atoms and optionally astarting gas containing hydrogen atoms (H) and/or halogen atoms (X) asconstituent atoms at a desired mixing ratio; a mixture of a starting gascontaining silicon atoms (Si) as constituent atoms and a starting gascontaining oxygen atoms and hydrogen atoms as constituent atoms also ata desired mixing ratio; or a mixture of a starting gas containingsilicon atoms (Si) as constituent atoms and a starting gas containingthe three atoms of silicon atoms (Si), oxygen atoms (O) and hydrogenatoms (H) as constituent atoms.

Alternatively, there may also be employed a mixture of a starting gascontaining silicon atoms (Si) and hydrogen atoms (H) as constituentatoms and a starting gas containing oxygen atoms (O) as constituentatoms.

More specifically, there may be mentioned, for example, oxygen (O₂),ozone (O₃), nitrogen monooxide (NO), nitrogen dioxide (NO₂), dinitrogenmonooxide (N₂ O), dinitrogen trioxide (N₂ O₃), dinitrogen tetraoxide (N₂O₄), dinitrogen pentaoxide (N₂ O₅), nitrogen trioxide (NO₃), and lowersiloxanes containing silicon atoms (Si), oxygen atoms (O) and hydrogenatoms (H) as constituent atoms such as disiloxane (H₃ SiOSiH₃),trisiloxane (H₃ SiOSiH₂ OSiH₃), and the like.

For formation of the layer region (O) containing oxygen atoms accordingto the sputtering method, a single crystalline or polycrystalline Siwafer or SiO₂ wafer or a wafer containing Si and SiO₂ mixed therein maybe employed as the target and sputtering of these wafers may beconducted in various gas atmospheres.

For example, when Si wafer is employed as the target, a starting gas forintroduction of oxygen atoms optionally together with a starting gas forintroduction of hydrogen atoms and/or halogen atoms, which mayoptionally be diluted with a diluting gas, may be introduced into adeposition chamber for sputtering to form gas plasma of these gases, inwhich sputtering of the aforesaid Si wafer may be effected.

Alternatively, by the use of separate targets of Si and SiO₂ or onesheet of a target containing Si and SiO₂ mixed therein, sputtering maybe effected in an atmosphere of a diluting gas as a gas for sputteringor in a gas atomsphere containing at least hydrogen atoms (H) and/orhalogen atoms (X) as constituent atoms. As the starting gas forintroduction of oxygen atoms, there may be employed the starting gasesshown as examples in the glow discharge method previously described alsoas effective gases in case of sputtering.

In the present invention, when providing a layer region (O) containingoxygen atoms during formation of the light receiving layer, formation ofthe layer region (O) having a desired depth profile in the direction oflayer thickness formed by varying the content C(O) of oxygen atomscontained in said layer region (O) may be conducted in case of glowdischarge by introducing a starting gas for introduction of oxygen atomsof which the content C(O) is to be varied into a deposition chamber,while varying suitably its gas flow rate according to a desired changerate curve. For example, by the manual method or any other methodconventionally used such as an externally driven motor, etc., theopening of certain needle valve provided in the course of the gas flowchannel system may be gradually varied. During this procedure, the rateof variation is not necessarily required to be linear, but the flow ratemay be controlled according to a variation rate curve previouslydesigned by means of, for example, a microcomputer to give a desiredcontent curve.

In case when the layer region (O) is formed by the sputtering method,formation of a desired depth profile of oxygen atoms in the direction oflayer thickness by varying the content C(O) of oxygen atoms in thedirection of layer thickness may be performed first similarly as in caseof the glow discharge method by employing a starting material forintroduction of oxygen atoms under gaseous state and varying suitably asdesired the gas flow rate of said gas when introduced into thedeposition chamber.

Secondly, formation of such a depth profile can also be achieved bypreviously changing the composition of a target for sputtering. Forexample, when a target comprising a mixture of Si and SiO₂ is to beused, the mixing ratio of Si to SiO₂ may be varied in the direction oflayer thickness of the target.

In the photoconductive member of the present invention, a substance (C)for controlling conductivity can also be incorporated in the first layerregion (G) containing germanium atoms and/or the second layer region (S)containing no germanium atom, whereby the conductivity characteristicsof said layer region (G) and/or said layer region (S) can be freelycontrolled as desired.

In the present invention, the layer region (PN) containing a substance(C) for controlling conductivity characteristics may provided at a partor the whole layer region of the light receiving layer. Alternatively,the layer region (PN) may be provided at a part or the whole layerretion of the layer region (G) or the layer region (S).

As a substance (C) for controlling conductivity characteristics, theremay be mentioned so called impurities in the field of semiconductors. Inthe present invention, there may be included p-type impurities givingp-type conductivity characteristics and n-type impurities giving n-typeconductivity characteristics to Si or Ge.

More specifically, there may be mentioned as p-type impurities atomsbelonging to the group III of the periodic table (Group III atoms), suchas B (boron), Al (aluminum), Ga (gallium), In (indium), Tl (thallium),etc., particularly preferably B and Ga.

An n-type impurities, there may be included the atoms belonging to thegroup V of the periodic table, (Group V atoms), such as P (phosphorus)As (arsenic), Sb (antimony), Bi (bismuth), etc., particularly preferablyP and As.

In the present invention, the content of the substance (C) forcontrolling the conductivity in the light receiving layer may besuitably selected depending on the conductivity characteristics requiredfor said light receiving layer or the characteristics of other layers orthe substrate provided in direct contact with said light receivinglayer, depending on the organic relation such as the relation, with thecharacteristics at the contacted interface with said other layers or thesubstrate.

When the above substance for controlling conductivity characteristics isto be incorporated in the light receiving layer locally at the desiredlayer region of said light receiving layer, particularly at an endportion layer region (E) on the substrate side of the light receivinglayer, the content of the substance for controlling conductivitycharacteristics is determined suitably with due consideration of therelationships with characteristics of other layer regions provided indirect contact with said layer region (E) or the characteristics at thecontacted interface with said other layer regions.

In the present invention, the content of the substance (C) forcontrolling conductivity characteristics contained in the layer region(PN) should preferably be 0.01 to 5×10⁴ atomic ppm, more preferably 0.5to 1×10⁴ atomic ppm, most preferably 1 to 5×10³ atomic ppm.

In the present invention, when the content of said substance (C) forcontrolling conductivity characteristics in the layer region (PN) ispreferably 30 atomic ppm or more, more preferably 50 atomic ppm or more,most preferably 100 atomic ppm or more, the substance (C) is desired tobe contained locally at a part of the layer region of the lightreceiving layer, particularly localized at the end portion layer region(E) on the substrate side of the light receiving layer.

In the above constitution, by incorporating the substance (C) forcontrolling conductivity characteristics in the end portion layer region(E) on the substrate side of the light receiving layer so that thecontent may be the above value or higher, for example, in the case whensaid substance (C) to be incorporated is a p-type impurity as mentionedabove, migration of electrons injected from the substrate side into thelight receiving layer can be effectively inhibited when the free surfaceof the light receiving layer is subjected to the charging treatment to ⊕polarity. On the other hand, in the case when the substance to beincorporated is a n-type impurity as mentioned above, migration ofpositive holes injected from the substrate side into the light receivinglayer can be effectively inhibited when the free surface of the lightreceiving layer is subjected to the charging treatment to ⊕ polarity.

Thus, in the case when a substance for controlling conductivecharacteristics of one polarity is incorporated in the aforesaid endportion layer region (E), the residual layer region of the lightreceiving layer, namely the layer region (Z) excluding the aforesaid endportion layer region (E) may contain a substance for controllingconductive characteristics of the other polarity, or a substance forcontrolling conductivity characteristics of the same polarity may becontained therein in an amount by far smaller than that practicallycontained in the end portion layer region (E).

In such a case, the content of the substance (C) for controllingconductivity characteristics contained in the above layer region (Z) canbe determined adequately as desired depending on the polarity or thecontent of the substance contained in the end portion layer region (E),but it is preferably 0.001 to 1000 atomic ppm, more preferably 0.05 to500 atomic ppm, most preferably 0.1 to 200 atomic ppm.

In the present invention, when the same kind of a substance forcontrolling conductivity is contained in the end portion layer region(E) and the layer region (Z), the content in the layer region (Z) shouldpreferably be 30 atomic ppm or less. As different from the cases asmentioned above, in the present invention, it is also possible toprovide a layer region containing a substance for controllingconductivity having one polarity and a layer region containing asubstance for controlling conductivity having the other polarity indirect contact with each other, thus providing a so called depletionlayer at said contact region. In short, for example, a layer containingthe aforesaid p-type impurity and a layer region containing theaforesaid n-type impurity are provided in the light receiving layer indirect contact with each other to form the so called p-n junction,whereby a depletion layer can be provided.

For incorporating a substance (C) for controlling conductivitycharacteristics such as the group III atoms or the group V atomsstructurally into the light receiving layer, a starting material forintroduction of the group III atoms or a starting material forintroduction of the group V atoms may be introduced under gaseous stateinto a deposition chamber together with the starting materials forformation of the second layer region during layer formation. As thestarting material which can be used for introduction of the group IIIatoms, it is desirable to use those which are gaseous at roomtemperature under atmospheric pressure or can readily be gasified atleast under layer forming conditions. Typical examples of such startingmaterials for introduction of the group III atoms, there may be includedas the compounds for introduction of boron atoms boron hydrides such asB₂ H₆, B₄ H₁₀, B₅ H₉, B₅ H_(ll), B₆ H₁₀, B₆ H₁₂, B₆ H₁₄, etc. and boronhalides such as BF₃, BCl₃, BBr₃, etc. Otherwise, it is also possible touse AlCl₃, GaCl₃, Ga(CH₃)₃, InCl₃, TlCl₃ and the like.

The starting materials which can effectively be used in the presentinvention for introduction of the group V atoms may include, forintroduction of phosphorus atoms, phosphorus hydrides such as PH₃, P₂H₄, etc., phosphorus halides such as PH₄ I, PF₃, PF₅, PCl₃, PCl₅, PBr₃,PBr₅, PI₃ and the like. Otherwise, it is also possible to utilize AsH3,AsF₃, AsCl₃, AsBr₃, AsF₅, SbH₃, SbF₃, SbF₅, SbCl₃, SbCl₅, BiH₃, BiCl₃,BiBr₃ and the like effectively as the starting material for introductionof the group V atoms.

The substrate to be used in the present invention may be eitherelectroconductive material or insulating material. As theelectroconductive material, there may be mentioned metals such as NiCr,stainless steel, Al, Cr, Mo, Au, Nb, Ta, V, Ti, Pt, Pd, etc. or alloysthereof.

As the insulating material, there may conventionally be used films orsheets of synthetic resins, including polyester, polyethylene,polycarbonate, cellulose acetate, polypropylene, polyvinyl chloride,polyvinylidene chloride, polystyrene, polyamide, etc., glasses,ceramics, papers and so on. These insulating substrates shouldpreferably have at least one surface subjected to electroconductivetreatment, and it is desirable to provide other layers on the side atwhich said electroconductive treatment has been applied.

For example, electroconductive treatment of a glass can be effected byproviding a thin film of NiCr, Al, Cr, Mo, Au, Ir, Nb, Ta, V, Ti, Pt,Pd, In₂ O₃, Sn₂, ITO (In₂ O₃ +SnO₂) thereon. Alternatively, a syntheticresin film such as polyester film can be subjected to theelectroconductive treatment on its surface by vacuum vapor deposition,electron-beam deposition or sputtering of a metal such as NiCr, Al, Ag,Pb, Zn, Ni, Au, Cr, Mo, Ir, Nb, Ta, V, Ti, Pt, etc. or by laminatingtreatment with said metal, thereby imparting electroconductivity to thesurface. The substrate may be shaped in any form such as cylinders,belts, plates or others, and its form may be determined as desired. Forexample, when the photoconductive member 100 in FIG. 1 is to be used asan image forming member for electrophotography, it may desirably beformed into an endless belt or a cylinder for use in continuous highspeed copying. The substrate may have a thickness, which is convenientlydetermined so that a photoconductive member as desired may be formed.When the photoconductive member is required to have a flexibility, thesubstrate is made as thin as possible, so far as the function of asubstrate can sufficiently be exhibited. However, in such a case, thethickness is preferably 10 μm or more from the points of fabrication andhandling of the substrate as well as its mechanical strength.

Next, an example of the process for producing the photoconductive memberof this invention is to be breifly described.

FIG. 17 shows one example of a device for producing a photoconductivemember.

In the gas bombs 1102-1106 there are hermetically contained startinggases for formation of the photoconductive member of the presentinvention. For example, 1102 is a bomb containing SiH₄ gas diluted withHe (purity: 99.999%, hereinafter abbreviated as "SiH₄ /He"), 1103 is abomb containing GeH₄ gas diluted with He (purity: 99.999%, hereinafterabbreviated as "GeH₄ /He", 1104 is a NO gas bomb (purity: 99.999%), 1105is a He gas bomb (purity: 99.999%) and 1106 is a H₂ gas bomb (purity:99.999%).

For allowing these gases to flow into the reaction chamber 1101, onconfirmation of the valves 1122-1126 of the gas bombs 1102-1106 and theleak valve 1135 to be closed, and the inflow valves 1112-1116, theoutflow valves 1117-1121 and the auxiliary valves 1132, 1133 to beopened, the main valve 1134 is first opened to evacuate the reactionchamber 1101 and the gas pipelines. As the next step, when the readingon the vacuum indicator 1136 becomes 5×10⁻⁶ Torr, the auxiliary valves1132, 1133 and the outflow valves 1117-1121 are closed.

Referring now to an example of forming a light receiving layer region onthe cylindrical substrate 1137, SiH₄ /He gas from the gas bomb 1102,GeH₄ /He gas from the gas bomb 1103, NO gas from the gas bomb 1104 arepermitted to flow into the massflow controllers 1107, 1108, 1109,respectively, by opening the valves 1122, 1123 and 1124 and controllingthe pressures at the outlet pressure gauges 1127, 1128, 1129 to 1 Kg/cm²and opening gradually the inflow valves 1112, 1113 and 1114,respectively. Subsequently, the outflow valves 1117, 1118, 1119 and theauxiliary valve 1132 are gradually opened to permit respective gases toflow into the reaction chamber 1101. The outflow valves 1117, 1118, 1119are controlled so that the flow rate ratio of SiH₄ / He gas, GeH₄ /Hegas and No gases may have a desired value and opening of the main valve1134 is also controlled while watching the reading on the vacuumindicator 1136 so that the pressure in the reaction chamber may reach adesired value. And, after confirming that the temperature of thesubstrate 1137 is set at 50°-400° C. by the heater 1138, the powersource 1140 is set at a desired power to excite glow discharge in thereaction chamber 1101, and at the same time depth profiles of germaniumatoms and oxygen atoms contained in the layer formed are controlled bychanging gradually the flow rates of GeH₄ /He gas and NO gas accordingto the change rate curve previously designed by operation of the valves1118 and 1119 manually or according to an externally driven motor, etc.

As described above, the first layer region (G)is formed to a desiredlayer thickness by maintaining the glow discharge for a desired periodof time. At the stage when the first layer region (G) has been formed toa desired thickness, following the same conditions and the procedureexcept for completely closing the outflow valve 1118 and changing thedischarging conditions, if desired, glow discharging is maintained for adesired period of time, whereby the second layer region (S) containingsubstantially no germanium atom can be formed on the first layer region(G).

For incorporating a substance (C) for controlling the conductivity intothe first layer region (G) and the second layer region (S), gases suchas B₂ H₆, PH₃, etc. may be added to the gases to be introduced into thedeposition chamber 1101 during formation of the first layer region (G)and the second layer region (S).

During layer formation, it is desirable to rotate the substrate 1137 ata constant speed by the motor 1139 in order to effect layer formationuniformly.

The present invention is further illustrated by referring to thefollowing Examples.

EXAMPLE 1

By means of the device shown in FIG. 17, samples of image formingmembers for electrophotography (Samples No. 11-1-17-3) (Table 2) wereprepared, respectively, on cylindrical aluminum substrates under theconditions shown in Table 1.

The depth profiles of germanium atoms in respective samples are shown inFIG. 18, and those of oxygen atoms in FIG. 19.

Each of the samples thus obtained was set in a charging-exposure testingdevice and subjected to corona charging at ⊕5.0 KV for 0.3 sec.,followed immediately by irradiation of a light image. The light imagewas irradiated by means of a tungsten lamp light source at a dose of 21lux sec through a transmission type test chart.

Immediately thereafter, ⊕chargeable developer (containing toner andcarrier) was cascaded on the surface of the image forming member to givea good toner image on the surface of the image forming member. When thetoner image was transferred on to a transfer paper by corona charging of⊕5.0 KV, a clear image of high density with excellent resolution andgood gradation reproducibility was obtained in every sample.

The same experiments were repeated under the same toner image formingconditions as described above, except for using GaAs type semiconductorlaser (10 mW) of 810 nm in place of the tungsten lamp as the lightsource, and image quality evaluation of toner transferred image wasperformed for each sample. As the result, an image of high quality,excellent in resolution and good in gradation reproducibility, could beobtained in every sample.

EXAMPLE 2

By means of the device shown in FIG. 17, samples of image formingmembers for electrophotography (Samples No. 21-1-27-3) (Table 4) wereprepared, respectively, on cylindrical aluminum substrates under theconditions shown in Table 3.

The depth profiles of germanium atoms in respective samples are shown inFIG. 18, and those of oxygen atoms in FIG. 19.

For each of these samples, the same image evaluation test was conductedas in Example 1 to give a toner transferred image of high quality ineach sample. Also, for each sample, usage test repeated for 200,000times was performed under the environment of 38° C. and 80% RH. As theresult, no lowering in image quality was observed in each sample.

                                      TABLE 1                                     __________________________________________________________________________                  Flow       Flow                                                                             Discharging                                                                          Layer forma-                                                                         Layer                               Layer Gases   rate       rate                                                                             power  tion rate                                                                            thickness                           constitution                                                                        employed                                                                              (SCCM)     ratio                                                                            (W/cm.sup.2)                                                                         (Å/sec)                                                                          (μm)                             __________________________________________________________________________    Layer (I)                                                                           SiH.sub.4 /He = 0.5                                                                   SiH.sub.4 + GeH.sub.4 = 200                                                              -- 0.18   15      5                                        GeH.sub.4 /He = 0.5                                                           NO                                                                      Layer (II)                                                                          SiH.sub.4 /He = 0.5                                                                   SiH.sub.4 = 200                                                                          -- 0.18   15     23                                        NO                                                                      __________________________________________________________________________

                  TABLE 2                                                         ______________________________________                                        Depth profile                                                                 of Ge                                                                         Depth   Sample                                                                profile of O                                                                          No.     1801   1802 1803 1804 1805 1806 1807                          ______________________________________                                        1901        11-1   12-1   13-1 14-1 15-1 16-1 17-1                            1902        11-2   12-2   13-2 14-2 15-2 16-2 17-2                            1903        11-3   12-3   13-3 14-3 15-3 16-3 17-3                            ______________________________________                                    

                                      TABLE 3                                     __________________________________________________________________________                                    Discharging                                                                          Layer forma-                                                                         Layer                           Layer Gases    Flow rate  Flow rate                                                                           power  tion rate                                                                            thickness                       constitution                                                                        employed (SCCM)     ratio (W/cm.sup.2)                                                                         (Å/sec)                                                                          (μm)                         __________________________________________________________________________    Layer (I)                                                                           SiH.sub.4 /He = 0.5                                                                    SiH.sub.4 + GeH.sub.4 = 200                                                              --    0.18   15      3                                    GeH.sub.4 /He = 0.5                                                           NO                                                                            B.sub.2 H.sub.6 /He = 10.sup.-3                                         Layer (II)                                                                          SiH.sub.4 /He = 0.5                                                                    SiH.sub.4 = 200                                                                          --    0.18   15     25                                    NO                                                                      __________________________________________________________________________

                  TABLE 4                                                         ______________________________________                                        Depth profile                                                                 of Ge                                                                         Depth   Sample                                                                profile of O                                                                          No.     1801   1802 1803 1804 1805 1806 1807                          ______________________________________                                        1901        21-1   22-1   23-1 24-1 25-1 26-1 27-1                            1902        21-2   22-2   23-2 24-2 25-2 26-2 27-2                            1903        21-3   22-3   23-3 24-3 25-3 26-3 27-3                            ______________________________________                                    

The common layer forming conditions in the above Examples of the presentinvention are shown below

Substrate temperature: Germanium atom (Ge) containing layer . . . about200° C. No germanium atom (Ge) containing layer . . . about 250° C.

Discharging frequency: 13.56 MHz

Inner pressure in reaction chamber during the reaction: 0.3 Torr.

The photoconductive member of the present invention designed to havesuch a layer constitution as described in detail above can solve all ofthe various problems as mentioned above and exhibit very excellentelectrical, optical, photoconductive characteristics, dielectricstrength and use environment characteristics.

In particular, the photoconductive member of the present invention isfree from any influence from residual potential on image formation whenapplied for an image forming member for electrophotography, with itselectrical characteristics being stable with high sensitivity, having ahigh SN ratio as well as excellent light fatigue resistance andexcellent repeated use characteristic and being capable of providingimages of high quality of high density. clear halftone and highresolution repeatedly and stably.

Further, the photoconductive member of the present invention is high inphotosensitivity over all the visible light region, particularlyexcellent in matching to semiconductor laser, excellent in interferenceinhibition and rapid in response to light.

I claim:
 1. A photoconductive member comprising a substrate forphotoconductive member and a light receiving layer provided on saidsubstrate having a layer constitution in which a layer region (G)comprising an amorphous material containing germanium atoms and at leastone of hydrogen atoms and halogen atoms and a layer region (S)exhibiting photoconductivity comprising an amorphous material containingsilicon atoms and at least one of hydrogen atoms and halogen atoms aresuccessively provided from the substrate side, said light receivinglayer having a layer region (O) containing oxygen atoms, the depthprofile of oxygen atoms in the layer thickness direction in said layerregion (O) having at least a part in which the distributionconcentration is increased smoothly and continuously toward the upperend surface of the light receiving layer.
 2. A photoconductive memberaccording to claim 1, wherein hydrogen atoms are contained in at leastone of the layer region (G) and the layer region (S).
 3. Aphotoconductive member according to claim 1, wherein hydrogen atoms arecontained in at least one of the layer region (G) and the layer region(S).
 4. A photoconductive member according to claim 1, wherein germaniumatoms are distributed ununiformly in the layer region (G).
 5. Aphotoconductive member according to claim 1, wherein germanium atoms aredistributed uniformly in the layer region (G).
 6. A photoconductivemember according to claim 1, wherein a substance (C) for controllingconductivity is contained in the light receiving layer.
 7. Aphotoconductive member according to claim 6, wherein the substance (C)for controlling conductivity is an atom belonging to the group III ofthe periodic table.
 8. A photoconductive member according to claim 6,wherein the substance (C) for controlling conductivity is an atombelonging to the group V of the periodic table.
 9. A photoconductivemember according to claim 1, wherein silicon atoms are contained in thelayer region (G).
 10. A photoconductive member according to claim 9,wherein the amount of germanium atoms contained in the layer region (G)is 1 to 1×10⁶ atomic ppm based on the sum of germanium atoms and siliconatoms.
 11. A photoconductive member according to claim 1, wherein thelayer region (G) has a layer thickness of 30 Å to 50 μ.
 12. Aphotoconductive member according to claim 1, wherein the layer region(S) has a layer thickness of 0.5 to 90 μ.
 13. A photoconductive memberaccording to claim 1, wherein there is the relationship between thelayer thickness T_(B) of the layer region (G) and the layer thickness Tof the layer region (S) of T_(B) /T ≦1.
 14. A photoconductive memberaccording to claim 3, wherein said halogen atoms are selected fromfluorine, chlorine, bromine and iodine.
 15. A photoconductive memberaccording to claim 1, wherein the content of oxygen atoms in the layerregion (O) is 0.001 to 50 atomic %.
 16. A photoconductive memberaccording to claim 15, wherein the upper limit of the content of oxygenatoms in the layer region (O) is 30 atomic %, when the layer thicknessT_(O) of the layer region (O) comprises 2/5 or more of the layerthickness T of the light receiving layer.
 17. A photoconductive memberaccording to claim 1, wherein 0.01 to 40 atomic % of hydrogen atoms arecontained in the layer region (G).
 18. A photoconductive memberaccording to claim 1, wherein 0.01 to 40 atomic % of halogen atoms arecontained in the layer region (G).
 19. A photocondutive member accordingto claim 1, wherein 0.01 to 40 atomic % in total amount of hydrogenatoms and halogen atoms are contained in the layer region (G).
 20. Aphotocondutive member according to claim 1, wherein 1 to 40 atomic % ofhydrogen atoms are contained in the layer region (S).
 21. Aphotoconductive member according to claim 1, wherein 1 to 40 atomic % ofhalogen atoms are contained in the layer region (S).
 22. Aphotoconductive member according to claim 1, wherein 1 to 40 atomic % intotal amount of hydrogen atoms and halogen atoms are contained in thelayer region (S).
 23. A photoconductive member according to claim 7,wherein the atom belonging to the group III of the periodic table isselected from among B, Al, Ga, In and Tl.
 24. A photoconductive memberaccording to claim 8, wherein the atom belonging to the group V of theperiodic table is selected from among P, As, Sb and Bi.
 25. Aphotoconductive member according to claim 1, wherein the light receivinglayer has a layer region (PN) containing a substnace (C) for controllingconductivity on the substrate side.
 26. A photoconductive memberaccording to claim 25, wherein the content of the substance (C) forcontrolling conductivity contained in the layer region (PN) is 0.01 to5×10⁴ atomic ppm.
 27. A photoconductive member according to claim 25,the substance (C) for controlling conductivity contained in the layerregion (PN) is 30 atomic ppm or more.
 28. A photoconductive memberaccording to claim 1, wherein the light receiving layer has a depletionlayer.